The Message of the Messenger is a Great News
Allah tells His Messenger to say to those who disbelieved in Allah, associated others in worship with Him and denied His Messenger: `I am a warner, I am not as you claim.'
وَمَا مِنْ إِلَـهٍ إِلاَّ اللَّهُ الْوَحِدُ الْقَهَّارُ
(and there is no God (worthy of worship) except Allah, the One, the Irresistible,) means, He Alone has subjugated and controlled everything.
رَّبُّ السَّمَـوَتِ وَالاٌّرْضِ وَمَا بَيْنَهُمَا
(The Lord of the heavens and the earth and all that is between them,) means, He is the Sovereign of all that and is in control of it.
الْعَزِيزُ الْغَفَّارُ
(the Almighty, the Oft-Forgiving.) means, He is Oft-Forgiving as well as being Almighty and All-Powerful.
قُلْ هُوَ نَبَأٌ عَظِيمٌ
(Say: "That (this Qur'an) is a great news,") means, `something very important, which is that Allah has sent me to you.
أَنتُمْ عَنْهُ مُعْرِضُونَ
(From which you turn away!) means, `you neglect it.'
مَا كَانَ لِىَ مِنْ عِلْمٍ بِالْمَـَلإِ الاٌّعْلَى إِذْ يَخْتَصِمُونَ
(I had no knowledge of the chiefs (angels) on high when they were disputing and discussing. ) meaning, `were it not for the divine revelation, how could I have known about the dispute of the chiefs on high (the angels)' This refers to their dispute concerning Adam, peace be upon him, and how Iblis refused to prostrate to him and argued with his Lord because He preferred him (Adam) over him. This is what Allah says:
In verse 69, it was said: مَا كَانَ لِيَ مِنْ عِلْمٍ بِالْمَلَإِ الْأَعْلَىٰ إِذْ يَخْتَصِمُونَ (I had no knowledge of the Heavenly Beings when they were debating (about the creation of 'Adam). Means: 'It is a clear proof of my prophethood that I am telling you these things from such a high assembly, things that cannot be found out through any medium other than wahy (revelation).' The words 'these things' refer to the conversation between Allah Ta’ ala and the angels at the time of the creation of Sayyidna 'Adam (علیہ السلام) and which finds mention in Surah Al-Baqarah where the angels had said: أَتَجْعَلُ فِيهَا مَن يُفْسِدُ فِيهَا وَيَسْفِكُ الدِّمَاءَ (They said, "Will You create there one who will spread disorder on the earth and cause bloodsheds...? - 2:30). This conversation has been expressed here through the word: اختصام (ikhtisam) which literally means 'quarrel' or 'debate' - although, the angels never posed that question in terms of some objection or debate, instead, they wanted to find out the wise consideration behind the creation of Sayyidna 'Adam (علیہ السلام) ، but the outward pattern of the questions and answers had taken the form of some sort of a debate, therefore, it was alluded to as 'ikhtisam' or debate. This is similar to a younger person questioning an elder person, who refers to that question and answer, in a frank and casual manner, as a debate or quarrel.
When the people who rejected the truth see their miserable lot in the Hereafter, they will remember those who had taken the side of the Truth and as such had come to be regarded as inferior in their society. The rejectors of the truth used to say of the supporters of truth that the latter disrespected the great ones; that they had deviated from their ancestral religion and had made their own path separate from that of the community.These rejectors of the truth had considered themselves to be on the right path. But in the Hereafter, the tables will be turned. At that time it will be clear to them that those whom they looked at with contempt and ridiculed, are the very people who are now enjoying the foremost position of success.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.